Mounting arrangement for coplanar grids having common flat strip cathode

ABSTRACT

A color television picture tube, having a plurality of electron guns delivering electron beams and a deflection device for causing the television screen to be swept by said beams, comprises means for supplying parallel and coplanar electron beams at their entrance into the deflection device and means imposing a delay on the video signals controlling two of the guns so that the three elements of a triad of elementary colors of the screen receive quantities of electrons according to the video information corresponding to one and the same televised dot.

United/States "[19 a Casset etal.

1 1 Nov. 5, 1974 [5 MOUNTING ARRANGEMENT FOR COPLANAR cams HAVING COMMONFLAT STRIP CATHODE Inventors: Georges Casset,

Issi-Les-Moulineauxj Jean-Pierre Driffort, Chate-Nay-Malabry; PierreLebel, Kremlin-Bicetre, all of France Ste dite France-Couleur, Paris,France Filed: Sept. 27, 1972 Appl. No.: 292,639

Related US. Application Data Division of Ser. No. 857,638, Sept. 10,1969, Patv No. 3,733,507.

[73] Assignee:

US. Cl. 213/411, 313/417 Int. Cl H0lj 29/02, H01 j 29/46 Field of Search313/69 C, 170

References Cited UNlTED STATES PATENTS 2,427,888 9/1947 Warren ..3l3/80Hegbar 313/69 R 2,758,234 8/1956 Hensel 313/69 C 3,215,880 11/1965Krackhardt 313/82 R 3,448,316 6/1969 Yoshida et a1 313/69 C PrimaryExaminer-Robert Segal Attorney, Agent, or Firm-Karl F. Ross; HerbertDubno 1 [57] ABSTRACT A color television picture tube, having aplurality of electron guns delivering electron beams and a deflectiondevice for causing the television screen to be swept by said beams,comprises means for supplying parallel and coplanar electron beams attheir entrance into the deflection device and means imposing a delay onthe video signals controlling two of the guns so that the three elementsof a triad of elementary colors of the screen receive quantities ofelectrons according to the video information corresponding to one andthe same televised dot.

2 Claims, 29 Drawing Figures PATENTEUNUY s 1974 I Bv-5 l l r-a r-s r-4r-3 M m i Y m z sr E l fig-6 uv 5I974 PATENTEI] ll was 7 3,846,659

SCANNING C URRE N T L INE-SCA NN/NG C URRE N T FRAME-SCANNING 4- CURRENTPATENTEDNUY 5mm x 3,846,659

USN?

MOUNTING ARRANGEMENT FOR COPLANAR GRIDS HAVING COMMON FLAT STRIP CATHODEPRIOR ART Numerous tubes having a plurality of electron beams have beenproposed for receiving color television pictures.

The majority of tubes proposed comprise three electron guns, eachcorresponding to a primary color, normally blue, green and red, the fluxof which is controlled respectively by video signals corresponding tothese colors, the beams passing through a scanning device or deflectorwhich causes them to sweep the screen of the tube.

The latter comprises triads of elements which light up respectively inblue, green and red under the impact of the beams, with an intensitywhich depends on the electron flux carried by the latter.

The majority of tubes used at present are of the shadow-mask type, i.e.,they contain a mask with hols, each corresponding to a triad of elementsof the screen,

through which the beams pass before impinging on the screen; aconvergence device trains the three beams through each of the holes inupon the several dots of a respective triad, thus ensuring coincidencebetween each of the beams and the triad element of the colorcorresponding to that beam.

Tubes are likewise used for receiving sets wherein the elements of thetriads are vertical bands and the electron beams then converge in thegap formed by the vertical wires of a grid brought to a potentialdifferent from that of the screen and likewise from that of the electronbeams.

One problem which arises for all these receivers is to avoid thedeformation of the images at the edges of the screen and to retain thepurity of the colors, and this is more difficult to solve the larger theangle of scanning and the more closely the screen surface approaches aplane.

SUMMARY OF THE INVENTION The tube for a color television receiveraccording to the invention enables a color television image to beobtained without difficulty on a flat screen of large dimensions with asweep of at least 1 satisfying the condition of purity of color whilebeing of a simpler and more economical construction than conventionaltubes of this character.

The color-television receiving tube according to the invention generatesa set of electron beams for the illumination of its screen which areparallel to one another and lie in one and the same plane, at least fromtheir entrance into the scanning device, and impinge simultaneously onthe elements of different triads, the video information which they carrybeing staggered in time to restore the coincidence between the dots ofthe televised object and the image dots on the screen.

The receiving tube according tothe invention may be constructed withouta dynamic convergence device, thus permitting a considerably more simpledesign than that of conventional tubes.

More particularly, our invention aims at providing an improveddeflecting device for such a tube to ensure correct scanning of thetelevision screen from parallel and coplanar electron beams suppliedthereto.

The tube may be of the shadow-mask type or of the grid type.

BRIEF DESCRIPTION OF THE DRAWING Illustrative embodiments of ourinvention will now be described with reference to the accompanyingdrawing in which: 7

FIG. 1 is a diagrammatic view of a portion of a tube of a colortelevision receiver according to the invention;

FIG. 2 is a diagram illustrating an electron-gun as sembly for the tube;

FIG. 3 is a diagrammatic view in perspective of a portion of a mask andof a screen;

FIG. 4 is a diagrammatic view in horizontal section, on a larger scale,of a portion of the mask and the screen of FIG. 3;

FIG. 5 is a diagrammatic view of the tube according to the invention foranother form of construction, some members having been omitted for thesake of clarity in the illustration;

FIG. 6 is a front view showing diagrammatically the position of the gunsof a tube as shown in FIG. 5;

FIG. 7 is a diagrammatic view, in horizontal section, similar to part ofFIG. 5 but with illustration of the beams and drawn to a larger scale;

FIG. 8 is a diagrammatic view in axial section of a deflector accordingto the invention;

FIGS. 9 to 12 are explanatory diagrams;

FIG. 13 is a top view ofa plate adapted for use in the manufacture of adeflector according to the invention;

FIG. 14 is a view in axial section of a deflector core equipped withplates as shown in FIG. 13;

FIG. 15 is a diagrammatic view in axial section of a deflection deviceaccording to the invention;

FIG. 16 is a diagrammatic front view of a portion of a device as shownin FIG. 15;

FIG. 17 shows, diagrammatically, the construction of a line-scanningdevice;

FIG. 18 shows, diagrammatically, the construction of a frame-scanningdevice;

FIG. 19 is a diagrammatic view, in cross section through the axis of thetube, of a device for modifying the paths of electron beams;

FIG. 20 is a similar view to FIG. 19 but for another form ofconstruction;

FIG. 21 is a view similar to the two previous Figures but showing yetanother embodiment in longitudinal section;

FIG. 22 is a view similar to the three previous Figures but showing afurther modification, likewise in longitudinal section;

FIG. 23 is a perspective view of part of an electronbeam generatoraccording to the invention;

FIG. 24 is a front view of a cathode support for such a generator;

FIG. 28 is a perspective view of an electron-lens assembly which can beassociated with this generator; and 1 FIG. 29 is a highly diagrammaticview of a receiving tube for color television equipped with such agenerator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, acolor-television-receiving tube according to the invention comprisesthree guns C C,,, C delivering electron beams F F, F,, respectively.

These electron guns have coplanar axes (FIG. 2) situated in a planeparallel to the major sides of the screen of the tube.

The guns C are so disposed that the beams F which they deliver convergeat a single point 13. These beams are subject to the action of meansrepresented diagrammatically by an electron lens 14 bending them in sucha manner that, beyond the lens 14, the three beams are propagated alongparallel and coplanar paths F F',,, F',, which pass through a scanningdevice comprising horizontal sweep means 15 and vertical sweep means 16diagrammatically operated by electromagnetic coils. I

The tube comprises a mask 17 (FIG. 3) and a screen 18. The mask 17 has amultiplicity of holes 19 each associated with a triad of circular areasor phosphor dots 20,, 20,, and 20, on the screen luminescingrespectively in green, in blue and in red under the impact of theelctrons.

7 Instead of lying at the corners of an equilateral triangle, however,as ina conventional mask-type television tube, the areas of a triad-havea horizontal linear distribution. A red area 20 is followed, inhorizontal al ign ment, for example by a green-area 20 in turn followedby a blue area 2 0,, wliichjis, again followed by a red area 20, etc..luxtaposed with this horizontal row of areas or phosphor dots isanotherhorizontal row comprising adjacent areas offset b'y the width of one Ihalf-area in relation to'the-areas inthe preceding row,

the blue area'being adjacent to redand green areas in the first row, thered area being adjacent to the green and blue areas in the first rowetc.A third horizontal row likewise comprises areas disposed side byside, the blue area being adjacent 'to the red and green areas in thesecond row, the red area being adjacent to green and blue areas in thesecond row etc. The holes 19 in the mask 17 are aligned horizontally inlike manner.

Likewise according to the invention, whereas the video signalcorresponding to red, for example, is applied directly to the gun Cwithout any delay, the video signals corresponding to the blue color areapplied to the gun C through a line L,, (FIG. 1) having a delay equal tothe time which an electron beam takes, in the course of the horizontalsweep, to pass from a position in which it falls on a red area 20, of atriad to a blue area 20,, of another triad in the same horizontal row.not necessarily adjacent. A line L,., applying the green video signalsto the gun C introduces a delay double that of the line L,,.

If P,; is the screen spacing, that is to say the distance separating twophosphor dots of the same color in two adjacent triads, and P is thedistance separating the axes of two successive perforations 19 in oneand the of the guns C and the construction of the electrostatic lens 14are selected in such a manner that the distance d between the axes ofthe beams F and F,, and between the axes of the beams F, and F satisfythe formula:

11:0 a/ ad 1.-

in which a is any integer with the exception of 3 and whole multiples of3. The value a may thus be equal to l, 2, 4 etc FIG. 4 shows, forexample, the axis a, of the electron beam corresponding to the red videosignal for a dot of the televised picture at a given moment and trainedon a red area 20, of the triad T,,, which is the fifth starting from thetriad T or central triad in the horizontal row comprising the area 20,At this moment, the beam corresponding to the gun C has an axis a, at adistance d from the axis a, and trained on the blue area 20,, of thecentral triad T while the beam corresponding to the gun C has an axisa',, at a distance of 2d from the axis a, and falling on the green area20 of the triad T- symmetrical with the triad T in relation to thecentral triad T The video signal corresponding to the red component of adot in the televised object is carried by the beam whose axis is at a',.It causes the quasipoint element 20, of the triad T to be illuminated inred. Because of the intervention of the delay line L,., it is only whenthe axis a,, of the beam F reaches the blue phosphor dot 20,, of thetriad T in the course of the horizontal sweep that the beam F',, willcarry the blue video signal for the same televised dot. Similarly,through the intervention of the delay line L... it is only when the axisa, of the beam F, has arrived at'the green phosphor dot 20, of the triadT in the course of the horizontal sweep that it will carry the greenvideo signal throughthe same televised dot.

Consequently, during the horizontal sweep, the three component elementsof the triad T, will receive the electron beams corresponding to thevideo signal of the televised dot not absolutely simultaneously but withthe delay introduced by the delay lines L,., L,, yet without theseminimum delays being noticed by the viewerbethree beams passing throughthe scanning device, the

receiving tube may operate without a dynamic convergence device. Notonly is the manufacture of the tube simplified but likewise thedifficulty in obtaining the purity of colors, originating from thedisturbing influ ence of the convergence device on the operation of thescanning device in a conventional'picture tube, is thus eliminated.

The methods of producing phosphors for the tube of a conventionalshadow-mask picture tube, using photographic techniques, may be appliedwith the same facility to the formation of the phosphors on a screen fora picture tube according to the invention.

Reference will now be made to FIGS. 5 to 7, relating to a tube of thegrid type according to the invention.

The tube-forming television pictures according to the invention,includes in this form of construction, a screen E (FIG. 5) of the typecomprising, side by side, triads T of vertical bands which light uprespectively in green, in blue and in red, under the impact of electronsand which have been designated B.,, B, and Br. The triads are adjacentand are distributed regularly with a spacing P E referred to as screenspacing. inside the tube and at a distance from the latter there is agrid G formed by a multiplicity of wires f, parallel to the bands B andequidistant between them, the distance between two successive wires(referred to as grid spacing P being less than the distance between twotriads of the screen (P P In many embodiments, the screen spacing P is0.81 mm and the grid spacing is 0.74 mm, and the distance between thegrid and the screen is of the order of 23 mm, these numericalindications having no limiting character. The screen is at a higherelectrical potential than the wires of the grid; for example it may beat 25 KV while the grid wires are at 7 KV, these numerical indicationshaving no limiting character.

The tube is equipped with three electron guns C C C,, correspondingrespectively to the three primary colors green, blue and red, and theiraxes av, ab and ar are in one and the same horizontal plane 110 (FIG.6), which is the median plane of the screen E. The gun C has its axissituated in the vertical median plane 111 of the screen E. In the formof construction described, the axes av, ab and ar converge at a point112 situated in the plane 111 inside the tube, well upstream of theplane of the grid G.

Divergent electrostatic or electromagnetic lens means, illustrateddiagrammatically at 113, are interposed in the paths of the electronbeams Fv, Fb and Fr supplied by the several guns and are so designedthat, at their exit, the electron beams have parallel axes, asillustrated diagrammatically at ab, a'v, a'r.

The parallel and coplanar electron beams with equidistant axes passthrough a deflector 114 illustrated diagrammatically by a horizontaldeflection coil 115 and a vertical deflection cell 116.

The arrangement of the election guns and the position of the lens means113 are such that the distance d between the axis a'v (FIG. 7) of thebeam Fv and the axis ab of the beam Fb, equal to the distance betweenthe axis ab and the axis a'r, satisfies the same formula as above, withP the grid spacing and P again the screen spacing.

The distance between two beams need not be an integer of the spacingbetween two grid wires.

In the absence of a supply current to the coils 115 and 116, the axis abencounters the central triad T of the screen E at its central band whichmay be the blue band BbO, for example, and is equidistant from the wiresf-l and f1 of the grid G situated immediately one at each side of thevertical plane 111.

The axis a'v, whose distance from the axis ab has the value dcorresponding to the above formula, then en counters the screen at agreen band, which is the band Bv-S, in the example illustrateddiagrammatically in FIG. 7, passing between the wires f5 and f-6 of thegrid, and the axis a'r encounters the screen at a red band, which is theband BrS in the example, the index number given each of the triads andtheir constituents bands denoting their position relative to the centraltriad while the positive or negative sign indicates whether they are tothe right or to the left of the latter. It will be understood that theillustration in FIG. 7 is very diagrammatic and that in reality thenumber of triads counted between the intersections of the beam axes inthe absence of any deflection may be different from, eg considerablygreater than, that which has been illustrated.

The unequivocal correspondence between the three beams and the threetypes of band of the triads is retained in the course of the sweep.

The speed of the horizontal sweep of the screen by the electron beams ismade uniform, in known manner, and the invention provides for applyingthe information to the central gun and to the left-hand gun in theconventional case of sweeping from left to right, in the presentinstance to the gun Cb and to the gun Cv, by means of lines Lb and Lvintroducing delays in relation to the conductor Lr used to apply theinformation to the gun Cr.

The time constant of the line Lb is equal to the time necessary for thebeam Fb to pass, in the course of the horizontal sweep, from theposition in which its axis ab intersects the plane of the grid betweenthe wires f-l and f1 to that in which its axis intersects the plane ofthe grid between the wires f5 and f6. The time constant of the line Lvis equal to double the time constant of the line Lb. Under thesecircumstances the signals pertaining to one and the same televised dotare delivered to one and the same triad.

In the example, a picture dot is composed of the triplet BrS, B125, Bv5,the screen being struct by the beams Fb and Fv, carrying the blue andgreen information corresponding to the same dot as the red informationof the beam Fr, after impingement of the beam Fr, in a precise mannerwith delays which are equal to the time constants but are absolutelynegligible in comparison with the duration of retinal persistance. Theimage of the triplet therefore appears to the viewer under precisely thesame conditions as in a conventional tube.

The tube according to the invention uses an improved deflection system,generating uniform fields, which includes a core or sleeve 220 (FIG. 8)of ferrite, in the form of a tulip, whose outer surface comprises acylindrical portion 221 connected to a substantially frustoconicalportion 222 joined in turn to a cylindrical portion 223 of largerdiameter. The inner surface of the core 220 comprises a rounded internalportion 224 connected to a substantially frustoconical portion 225joining to the cylindrical portion 223 along an annular edge 226 havinga small radius of curvature in cross section. The axial dimension of thecore 220 is relativey short; it may, for example, be of the order ofhalf the diameter of the external edge 226, this indication having nolimiting character. The core converges axially from its sharp-edged end226 to a flat end face 227 of reduced diameter.

The invention provides for the use of such a core, or a similar one, incombination with a vertical deflection coil and a horizontal deflectioncoil both of which consist, in principle, of a single layer of wirewinding 228 shaped by the actual outline of the core in cross section.

In designing the coils, both for the horizontal and for the verticaldeflection, we start from a ferrite core or the like as described aboveon which there is formed a first single-layer winding, with a sinusoidaldistribution of its turns, and a second single-layer winding, also witha sinusoidal turn distribution, the regions of greater turn density inthe two windings being in mutually orthogonal radial planes. The firstwinding is energized by the horizontal deflection current and the secondwinding is fed by the vertical deflection current.

A flat-screen television picture tube is equipped with such a deflectorso positioned as to be traversed by the electron beams F F,,, F, or(FIGS. 1 or 5) at a point where their axes are parallel to one another,after passage of the beams throughthe divergent electrostatic orelectromagnetic lens 14 or 113.

FIG. 9 illustrates, in heavy solid lines, the outline of the picture orframe traced as one beam, upon passage through the grid f (in the caseof a grid-type) on the screen E comprising triads of parallel bands Bv,Bb, Br, this beam being emitted by a lateral gun, for example the gun Cvof FIG. 5 generating the green image; the picture tube comprises means,known per se, whereby, despite the flat screen, the upper and lowerlimits of the frame are horizontal lines h h The lateral limits aretherefore greatly curved lines, one concave towards the outside anddesignated 1 the other convex towards the outside and labeled [2;- Theframe, that is to say the outline of the image, supplied by the otherlateral gun Cr, associated with the red color, is illustrated in thinsolid lines; its upper and lower horizontal limits r and r then coincidewith lines It and hg but have been illustrated slightly spaced therefromin order to distinguish them on the Figure; the lateral limits arecurved lines 1,, and 1 whose curvatures are opposed to those of thelines I and I with which they have common ends d e, and d e The mediansweep lines thus obtained respectively by the green" and the red beamare illustrated at m,- and m,. These scanning lines have reversecurvatures and their maximum distance k, along the horizontal median, isthe same as the maximum distances of the lines I and I on the one handand t and 1 on the other hand on said that median.

The outline of the portion of the television screen swept by the greenbeam is as shown in heavy dotted lines when, in accordance with theinvention, the winding mode for the turns of the vertical-deflectionwinding is modified so that the corresponding lines of force of thefield, instead of being substantially parallel as with a winding havingturns distributed in accordance with sinusoidal laws, are in the form ofa barrel centered on a horizontal axis, as illustrated diagrammaticallyin FIG. 10, so that the upper limit of the outline passes from thehorizontal line 11 to the oblique line h',,., the lower limit becomingthe oblique line h' symmetrical thereto with respect to the horizontalmedian of the screen, the frame thus assuming the shape of a trapezoidconverging to the left, its left-hand limit I being simultaneouslystraightened to become the vertical straight line I',,., the otherlateral limit becoming the vertical straight line 1' at the same time.

The modification to which the area of the screen illuminated by the redbeam is subjected for this distribution mode of the turns of thevertical deflection winding is shown in thin dotted lines in FIG, 9: theframe has assumed a trapezoidal shape converging to the right, thepassage from the horizontal line 11 to the oblique line 11' taking placethrough rotation in clockwise direction. The major base t',, of the redtrapezoid is here on the left and its minor base t' is on the right. Thedistance between the adjacent bases of the two areas remains the maximumdistance k between the apices of the curved boundaries of the areaswhose limits have been drawn in full lines.

A modification of the distribution mode for the turn of the verticaldeflection winding which would lead to a field no longer in the form ofa barrel' but in the form of a cushion (i.e., with concave rather thanconvex curvature) would cause opposite distortions to some extent; thegreen frame would converge to the right and the red frame to the leftbut their lateral limits would not be straightened.

FIG. 11 illustrates, with similar references and the same training oflines as in FIG. 9 thick or thin, the shape of the green and red framesrespectively, for a sinusoidal distribution of the turns of the coilsfor both horizontal and vertical deflection. The dotted outlines relateto a law of distribution of the turns of the horizontal-deflectionwinding whereby the lines of force of the corresponding field are notsubstantially parallel but, on the contrary, assume a barrel shape asillustrated diagrammatically in FIG. 12, in such a manner that the greenarea bounded by an upper the line 12" and a lower line 11" convergesleftward; the red frame has rightwardly converging upper and lowerlimits 11",, and 11" The lateral limits t,,, and t" of the green areaare not straightened and the whole of the green area is displaced towardthe left. The left-hand lateral limit of the red area t' is symmetricalwith its boundary 1" with reference to the median vertical plane of thescreen, and the right-hand limit t" is symmetrical with to boundaryt",,. with respect to the same vertical plane. But whereas the laterallimits I and 1 of the original red area were to the left of the laterallimits I and t of the original green area, a relative displacement hastaken place in the horizontal direction and in the example illustratedin FIG. 11 it has been sufficient for the lateral limits t",,. and t" ofthe green area to have come to lie, after modification of the mode ofturn distribution, to the left of the corresponding lateral limits t",,and t" of the red area. The distance k between the lateral limits hasbecome very small in the Figure and is now of opposite sign.

We have found that it is possible, by modifying the mode of distributionof the turns of both the vertical deflection and thehorizontal-deflection coil, as described above, to obtain green and redareas substantially coinciding with the rectangular blue area providedby the central gun, and therefore to obtain a satisfactory colortelevision picture both with regard to the convergence and with regardto the purity of the colors.

We therefore provide, after determination of these laws of distribution,an annular plate 230 (FIGS. 13 and 14) having a peripheral flange 231with radial slots 232 representing the distribution mode for the turnsof the line-deflection winding as determined above, this plate coveringthe face 227 of the core 220 as shown in FIG. 14. We further provide ofa ring 233, adapted to cover the large-diameter rim 226 of the core 220and comprising at its edge 234 an array of radiating slots .representingthe same law of succession. The construction of a line deflectionwinding then takes place by stretching the conductor 228 (FIG. 8) aroundthe toroidal body constituted by the assembly of the core 220, the plate230 and the ring 233, with insertion of that conductor into successiveslots in the plate 230 and in the ring 233.

The same procedure is followed for the construction of the framedeflection winding.

Reference will now be made to FIG. 15, relating to a deflector deviceaccording to the invention for a form of construction particularly wellsuited to colortelevision picture tubes wherein the parallel coplanarelectron beams entering the deflector are relatively far apart. In thisform of construction, a ferrite-core deflector as described above iscombined with a single coil 251 energized by fed from theframe-deflection current and influencing the beams before they reach thedeflector. The coil 251 may advantageously be produced by placing atoroidal winding of wire in a single layer around a former 252, forexample one having a substantially rectangular cross-section, which maybe of non-magnetic material. The coil 251 is composed of two groups ofturns 253 and 254 (FIG. 16) distributed one at each side of the medianhorizontal plane and connected in series, the lines of force of thefield inside the coil 251 .being strongly cushion-shaped or outwardlyconcave as represented by the arrows in FIG. 16.

The effect of such a coil is studied by combining it with a maindeflector with a toroidal core, as described above, wherein the turnsboth of the line-deflection coil and of the frame deflection coil aredistributed in accordance with a sinusoidal law.

We have found that, simply by selection of the number of turns in thegroups 253 and 254 and by modifying the distribution laws for the turnsof each of the deflection coils of the main deflector, we can realize adeflecting device satisfying the strictest conditions for obtaining asuitable color-television picture, even with electron beams spaced 5.6mm apart at the entrance to the device.

We prefer to use a relatively fine wire, for example one having adiameter of0.5 mm, both for the windings of the deflection coils of themain deflector and for that of the coil 251 serving as a preliminarydeflector. The winding of the latter may then be made with contiguousturns.

FIG. 17 illustrates diagrammatically the construction of aline-deflection device formed from a first half-coil 240 and a secondhalf-coil 241 disposed symmetrically one at each side of the diametralvertical plane; each of the halfcoils comprises twenty-two turns perquadrant, for a total of 88 turns, bunched about the horizontaldiametral plane P, and the following Table I shows the distributionofthe turns over 90, the number in the first column showing the ordernumber of the turns (1 indicates the first turn; 2 indicates the secondturn etc... the second column showing the angular spacing between theturn and the plane of reference.

The construction of the winding of the frame deflection coil isillustrated in FIG. 18. The turns are counted angularly from a referenceposition coinciding with the diametral vertical plane. A first half-coil245 is symmetrical to a second half-coil 246 in relation to thehorizontal diametral plane; the distribution of the twentyfive turns perquadrant, corresponding to a total of 100 turns, is given in theaccompanying Table II in which the figures in the first column representthe order number of the turns and the figures in the second columnindicate the angular spacing of the turns in relation to the verticalplane of reference.

As will be apparent from Table l, the two symmetrical halves of thehorizontal-deflection coil 240, 241 (FIG. 17) are separated by a pair ofwide gaps, each amounting to 2 X (4835) 8250. The gaps between thehalves 245, 246 of the vertical-deflection coil (FIG. 18) amount each to2 X (90 7437) 3046, each of these halves being divided into a pair ofquadrantal subgroups separated by gaps amounting each to 2 X 609 l2l8.

While the coil 251 of HG. 16 is shown to be generally coextensive withthat of coil 240, 241, it should be noted that the line-scanning currenttraverses the two halves of the latter coil in parallel whereas theframescanning current, partly passing through coil 251 as de scribedabove, enters the two halves 253, 254 in a series-opposed relationshipas far as the vertically oriented magnetic field is concerned. Thus, thelines of force generated thereby are outwardly concave, as shown in FlG.16, rather than outwardly convex, as illustrated in FlG. 12 for thefield generated by the coil 240, 241. The supplemental magnetic fieldthus generated is effective in the plane of beam separation, i.e., thehorizontal plane 10 (FlG. 2) of (FIG. 6) coinciding with the plane P ofFIG. 17.

All the coils and single-layer windings have a sufficiently lowimpedance to be able to be connected to transistors without theinterposition of adaptors. The deflector device according to theinvention is therefore suitable for inclusion in a transistorisedcolor-television receiver.

Reference will now be made to FIG. 19, relating to a realization of anelectromagnetic lens 14 or 113. The convergent beams F and F, aresubject to the action of magnetic fields illustrated diagrammatically bythe lines of force 30 and 31 developed by electromagnets 32 and 33outside the neck 34 of the tube, their arcuate coils 35 and 36 beingsurrounded by windings 37 and 38 through which a direct current flows.The path of the central beam F remains unaffected by the fields 30 and31 which are disposed symmetrically, the poles of the same sign of thetwo electromagnets being substantially diametrically opposite oneanother.

Reference will now be made to FIG. 20. ln this embodiment, the beam F,\is influenced by its passage between two parallel plates 40 and 41, of amagnetic material having a low remanence, which are extended by twohorns 42 and 43, respectively; opposite the two horns are situated thepolar ends 45 and 46 of an electromagnet 44 mounted outside the neck 34.

The arrangement for the beam F,- is symmetrical to the previous one inrelation to the vertical plane 11.

The beam F, is surrounded by a shield 47 while pass- .ing through theregion of the tube bounded by the plates 40 and 41.

In the embodiment shown in FIG. 21, the guns C C C, emit, through theirend grids, into a common grid 50 of cylindrical shape maintained, at thesame potential as the end grids. The grid 50 is followed by another grid51, likewise cylindrical but brought to a potential different from thatof the grid 50.

In the form of construction shown in FIG. 22, the beam F, leaving thegun C, is subject to the action of two parallel plates 52 and 53respectively carrying positive and negative electrical charges.Similarly, the beam Fr is subject to the action of two plates 54 and 55respectively charged negatively and positively.

The action of the plates 52-55 on the beams F, and F renders themparallel to the central beam F,,.

A further feature of our invention resides in an im proved generator ofparallel and coplanar electron beams, leading to a considerableadditional simplification in the manufacture of a tube, eliminating thenecessity for an electron lens, and supplying beams with a precision inpositioning greater than that which could be obtained hitherto.

The generator of parallel electron beams according to the inventioncomprises a cathode 310 (FIG. 23) which may be of the type used inmultielectrode electron tubes in the form of a hollow prismatic stripwith two large lateral faces 311 and 312 (FIG. 26) and two small faces313 and 314. One of the large faces, for example the face 312, iscovered with a layer of barium carbonate. Mounted inside the cathode310, with two parallel strands, is a heating filament 315 covered withan insulator 316.

At each of its ends, the electrode 310 is mounted in an insulatingsupport 317 (FIG. 24), of generally rectangular shape but having, at itslonger bottom side 318, a narrower tab 319 defining two shoulders 320and 321, the opposite side bearing the reference numeral 322 while theshorter upright sides are designated 323 and 324. The insulating support317, preferably of mica, has, in its central portion, in the vicinity ofits connection to the tab 319, a rectangular window having sides 326,327, 328 and 329 through which the cathode 310 passes; a rigidconnection therebetween may be obtained by crimping. The mounting of thecathode 310 in the opposite plate (not shown) is similar except that thecathode 310 passes freely through the latter plate.

The support 317 bears against two uprights 330 and 331 rising from ametal base plate 332 confronting the face 312 of the cathode 310 (FIG.26) and having a rectangular notch 333 (FIG. 25) for the passage of thetab 319, the regions 334 and 335 of the plate 332 receiving theshoulders 320 and 321 of the support 317.

The plate 332, comprises lateral extensions 336 and 337, whose edges 338and 339 have a curved notch 340 and 341, respectively, bounded by lugs342 and 343.

Fixing takes place by embedding the extensions or feet 336 and 337 insealing webs 345 (only one shown) of glass, the lugs 342 and 343 and thenotch 340 or 341 forming an effective anchorage.

The lateral base plate 332 is adjacent to a central plate 346, in theform of an elongated rectangle, terminating in lugs 347 and 348 whichdefine a notch 349 and are fixed in the same sealing web 345. A gap 350is provided between the central plate 346 and the lateral plate 332.Adjacent to the plate 346 but separated from it by a gap 351, is a plate352 similar to the plate 332, likewise sealed by its ends in the webs345. The plate 352 comprises uprights 353 and 354 similar to theuprights 330 and 331 and serving to carry the aforementioned secondcathode-supporting plate similar to the insulating support 317.

In line with the cathode 310, the plates 332, 346 and 352 have holes,355, 356 and 357, respectively, whose axes lie in a common plane.

When the assembly is under vacuum, as for example in a tube, and anappropriate heating current flows through the filament 315, the face 312of the cathode 310 emits electrons and the plates 332, 346 and 352 withtheir respective holes 355, 356 and 357 act as Wehnelt cylinderscontrolling, for example by means of the potentials applied to theseWehnelt cylinders, the intensity of the electron beams passingrespectively through the holes 355, 356 and 357.

This arrangement affords convenient equalization of the distance betweenthe Wehnelt cylinders 332, 346, 352 and the confronting'face 312 of thecathode 310, with greater precision than for the distances between threeseparate cathodes of three electron guns and the corresponding Wehneltcylinders.

Moreover, only a single cathode has to be heated instead of threecathodes in the case of a three-gun generator with, in consequence, notonly a lower current consumption but above all a much smaller quantityof heat to be dissipated, less pollution of the tube and improvedstability of the latter.

The self-pollution of the conventional cylindrical cathode, whichnormally occurs in the course ofthe exhausting step, is considerablyreduced because of the apertures provided around the cathode.

In order to prevent the dispersion of the electrons outside the beams, ashielding device 360 is provided at each end of the cathode (FIGS. 26and 27), comprising a wall 361 parallel to the large faces of thecathode and perpendicular walls 362 and 363.

Reference will now be made to FIG. 28. A metal block 370, ofnon-magnetic material, is drilled with three bores 371, 372 and 373whose parallel and coplanar axes 374, 375 and 376 pass through thecenters of the holes 355, 356 and 357 of the Wehnelt cylinders (FIG. 23)and through the centers of respective holes 377, 378 and 379 formed in aplate 379' and constituting individual grids (collectively designated Gfor the electron beams.

Such a drilled block 370, brought to a suitable potential, acts as alens assembly 6, for the electron beams passing through the Wehneltcylinders and the multiple grid G The precision of the bores 371, 372and 373 is greater than that realizable with separate tubes, such asthose normally used as electron lenses in electrongun generators.

Such a lens device may be followed by another lens device 380, ofsimilar construction, with three bores 381, 382 and 383 whose axes 384,385 and 386 are aligned with the axes 374, 375, 376, the block Gconstituting the device 380 being held at a potential different fromthat of the block 370.

The assembly of the two drilled blocks advantageously replaces the twogroups of tubes normally following the first two grids G, and G, of amultipleelectron-beam generator, for example with an array of separateelectron guns. A precise positioning of the confronting faces 387 and388 of the blocks 370 and 380 is obtained without difficulty. Equallysatisfactory precision is easily obtained with regard to the position ofthe plate 379' forming the triple grid G A generator of multipleparallel electron beams as described may advantageously be included inthe construction of a television picture tube, particularly acolor-television tube; the video information corresponding to the threeprimary colors is then applied, for example, the plates acting asWehnelt cylinders.

Such a tube is illustrated very diagrammatically in FIG. 29. Thegenerator 390 according to the invention delivers three electron beams391, 392, 393 which are cylindroconical after passing throughelectron-lens devices (l -G and whose axes are parallel to one another.The three beams carry the information corresponding respectively to thethree primary colors. Their axes are coplanar and they are parallel asthey pass through the deflection device, represented diagrammatically bytwo coils 395 and 396, which is preferably of the type described abovewith reference to FIGS. 16 to 18. The coplanar and parallel scanningbeams fall on the television screen 398 after passing through a grid399.

The parallelism of the coplanar beams passing through the deflectiondevice 395, 396 dispenses with the need for the dynamic convergencemeans conventional in color-television picture tubes.

The single-cathode generator according to the invention enables beams tobe generated with closely juxtaposed axes, thus reducing the aberrationsin deflection.

This type of generator may also be included in the construction of amultiple-beam oscillograph tube.

What we claim is:

l. in a color-television picture tube including a screen withluminescent triads of primary colors and a plurality of electron gunswith coplanar parallel axes trained upon said screen. the improvementwherein said electron guns comprise a flat strip with anelectron-emissive surface forming a common cathode, mounting means forsaid strip, a plurality of metal plates adjoining each other withboundaries transverse to said strip in a plane parallel to saidelectron-emissive surface, said plates being provided with respectiveperforations confronting said electron-emissive surface, and retainingmeans securing said plates to one another and to said mounting meanswith said perforations in mutual alignment; said plates including twoouter plates and one intermediate plate, said mounting means comprisinga pair of end supports for said strips interlockingly engaging saidouter plates, said retaining means comprising a fusible body sealinglyanchored to extremities of all said plates; said extremities havingedges imbedded in said body, said edges forming recesses flanked byconverging jaws.

2. The improvement defined in claim I wherein said fusible body consistsof glass.

1. In a color-television picture tube including a screen withluminescent triads of primary colors and a plurality of electron gunswith coplanar parallel axes trained upon said screen, the improvementwherein said electron guns comprise a flat strip with anelectron-emissive surface forming a common cathode, mounting means forsaid strip, a plurality of metal plates adjoining each other withboundaries transverse to said strip in a plane parallel to saidelectron-emissive surface, said plates being provided with respectiveperforations confronting said electronemissive surface, and retainingmeans securing said plates to one another and to said mounting meanswith said perforations in mutual alignment; said plates including twoouter plates and one intermediate plate, said mounting means comprisinga pair of end supports for said strips interlockingly engaging saidouter plates, said retaining means comprising a fusible body sealinglyanchored to extremities of all said plates; said extremities havingedges imbedded in said body, said edges forming recesses flanked byconverging jaws.
 2. The improvement defined in claim 1 wherein saidfusible body consists of glass.